I'm trying to code an application which runs un different java platforms like J2SE, J2ME, Android, etc. I already know that I'll have to rewrite most of the UI for each platform, but want to reuse the core logic. Keeping this core portable involves three drawbacks that I know of: Keeping to the old Java 1.4 syntax , not using any of the nice language features of Java 5.0 only using external libraries that are known to work on those platforms (that is: don't use JNI and don't have dependencies to...

Hey fellows, Because calling a flush() to get every entities persist from memory to database. So if I use call too much unnecessary flush(), it could take much time therefore not a good choice for the performance. Here is a scenario that I don't know when to call a flush()? //Order and Item have Bidirectional Relationships Order ord = New ord("my first order"); Item item = New Item("tv",10); //...process item and ord object em.persist(ord);//em is an instance of EntityManager em.flush();// No.1...